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Forum—Quest for Methyl Bromide
Alternatives Continues
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America has made a commitment to the
world—for the protection of our planet's environment—to give up
nearly every outdoor, on-farm use of one of agriculture's most versatile and
effective chemicals: methyl bromide. Primarily through its chief scientific
branch—the Agricultural Research
Service—USDA is making an all-out, nationwide effort to help growers
farm successfully without this invaluable tool.
The research is, in fact, one of ARS' highest priorities. Scientists at 20
laboratories around the country are racing against the formidable deadlines of
the methyl bromide phaseout. They must come up with new tactics to help growers
combat the microbial, weed, and insect pests that methyl bromide so adeptly
thwarts.
For decades, most of America's strawberry growers have fumigated their fields
with methyl bromide to torpedo weed seeds and quash soil-dwelling pests that
could otherwise weaken or kill strawberry plants. Some of the California
studies that ARS has initiated to find new ways to farm the fruit are
highlighted in this issue (see page 4).
When methyl bromide is used to produce berries, bell peppers, or any of about
100 other crops, some of it escapes from the soil into the atmosphere. It
eventually reaches the stratosphere, where it causes a thinning of the ozone
layer. This damage reduces the layer's effectiveness in protecting us from
ultraviolet radiation.
To limit the flow of methyl bromide into the atmosphere, growers usually place
plastic tarpaulins over their fields after fumigation. At Riverside,
California, we are exploring a new option—"virtually impermeable
films." In lab tests, emissions of several promising fumigants were
reduced to a mere 5 to 15 percent with these films—as were emissions of
methyl bromide. The films may be useful not only for capturing the alternative
chemicals but also for minimizing methyl bromide emissions until the phaseout
is complete.
In Florida, we're tackling the challenge of how to grow tomatoes without the
protection methyl bromide affords. Growers there use about a third of all the
methyl bromide sold in this country for fumigating soils. Scientists at our
Fort Pierce laboratory have teamed with colleagues at the University of Florida
to work out a new regimen that relies on a trio of alternative
chemicals—Telone (1,3-dichloropropene), chloropicrin, and pebulate.
Tomatoes aren't harmed by pebulate, but other key crops are. That means this
trio isn't the answer for growing bell peppers, eggplant, or strawberries, for
instance. Our search continues for new, safe, and powerful ways to disinfest
fields where these crops are planted.
Launching the new tactic for Florida's tomato fields didn't happen without a
great deal of effort. At the outset of the research, pebulate wasn't approved
by the U.S. Environmental Protection Agency (EPA) for use in fields where
tomatoes would be hand-transplanted. Yet hand-transplanting is the method
nearly all of tomato producers in Florida use to establish young nursery-grown
plants.
Through the efforts of the USDA/EPA Methyl Bromide Alternatives Working Group
and pebulate's manufacturer, Zeneca, Inc., the product is now conditionally
registered for this much-needed use. The pebulate saga is a success the
committee hopes to repeat with other compounds that may be appropriate
alternatives to methyl bromide yet currently lack the requisite federal and
state registrations.
Another chemical that has attracted the committee's interest is propargyl
bromide, a fumigant that kills nematodes, weeds, and soil-dwelling fungi. To
bolster ARS and university research on this compound, USDA recently allocated
$800,000 specifically for propargyl bromide studies.
Will alternatives developed in the laboratory succeed in real-world conditions?
To ensure that they do, ARS includes grower-managed demonstration plots as a
key part of the methyl bromide alternatives research program. California's
commercial and organic strawberry farmers have volunteered portions of their
fields for this work, as have growers of grapes, peaches, and
almonds—other crops that will be affected by the looming loss of methyl
bromide. Similarly, Florida tomato and pepper producers have opened their farm
gates to researchers.
Growers can learn about research results at field days regularly offered at
these demonstration sites. What's more, we present the latest updates in
Methyl Bromide Alternatives, a quarterly newsletter sent free-of-charge
to growers, researchers, and others. The newsletter also appears on the World
Wide Web at http://www.ars.usda.gov/is/np/mba/mebrhp.htm.
And scientists from the United States and abroad summarize their findings every
year at the Annual International Research Conference on Methyl Bromide
Alternatives and Emissions Reduction, which USDA cosponsors. Held in either
Orlando, Florida, or San Diego, California, every year since 1994, this
symposium has become the world's premier forum on the topic.
To find substitutes that match the efficacy and versatility of methyl bromide
is, without doubt, a monumental challenge for scientists and growers alike. We
continue to give it all we've got.
Kenneth W. Vick
ARS National Program Leader
Post-Harvest Entomology
Beltsville, Maryland |
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"Forum" was published in the
January 2001
issue of Agricultural Research magazine.
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